CKAN uses its internal model to store metadata about the different records, and presents it on a web interface that allows users to browse and search this metadata. It also offers a powerful API that allows third-party applications and services to be built around it. - See more at: http://ckan.org/developers/about-ckan/#sthash.tq9dKkRl.dpuf
Here are some sites using CKAN to deliver data.
CKAN is supported by http://OKFN.org